Retention of thermoplastic material on pulp by a reaction product of a nitrogenous base and a salt of carboxylic acid



United States Patent Office 3,11%,731 Patented Jan. 28, 1964 a fibrous body and to More particularly, the

The present invention relates to a method of making the same.

present invention is concerned with a fibrous body which consists of a mixture of fibers and of thermoplastic synthetic non-fibrous material.

It is known to produce highly resilient paper of great Wet strength by mixing the fibrous pulp in the hollander with a suspension of synthetic material such as a suspension of polyvinylalcohol, or with latex, and to produce paper from the thus formed mixture. Other mixtures of fibrous material and synthetic plastics have been used to produce industrial materials of various types, whereby for instance polyvinylchloride, polystyrene resins or other polymerization products are mixed with fibrous materials and the mixture is then compressed and/ or hardened under pressure and at elevated temperatures.

These methods of producing a shaped body which consists essentially of a mixture of fibrous material and nonfibrous synthetic or natural plastic, whereby as natural plastic material primarily latex is to be considered, all show relatively insumcient fixation of the plastic material on the fiber and, consequently, only a relatively small portion of the plastic material which initially is introduced in the form of an emulsion or the like, will be adhered to the fibrous material while a relatively large portion of the plastic materials will remain suspended and Will be withdrawn with the liquid portion of the pulp. This does not only lead to a relatively high loss of plastic material but causes also considerable difficulty with respect to the removal of liquid from the pulp-plastic material mixture. Furthermore, frequently, foaming occurs when a relatively large portion of the suspended material is not adhered to the fibers of the pulp.

It is therefore an object of the present invention to overcome the above-discussed disadvantages of the prior art methods.

It is another object of the present invention to provide a method of producing a shaped body which consists essentially of an intimate mixture of a fibrous material and of a thermoplastic material, which body contains a relatively large proportion of thermoplastic material adhered to the fibrous material and can be produced in a simple and economical manner.

it is a further object of the present invention to provide a sheet-like body, consisting essentially of an intimate mixture of a fibrous material and of a relatively large proportion of a plastic non-fibrous material.

Other objects and advantages of the present invention will become apparent from a further reading of the description and of the appended claims.

With the above and other objects in view, the present invention contemplates in a method of producing a shaped body consisting essentially of an intimate mixture of a fibrous material and a thermoplastic material interposed between and adhering to the fibers of the fibrous material, the steps of introducing into a fibrous pulp consisting essentially of a suspension of fibers in water finely subdivided thermoplastic material, a water-soluble nitrogenous base of high molecular weight and a water-soluble salt of a carboxylic acid of high molecular weight, so as to form on the fibers a water insoluble reaction product of the nitrogenous base and the salt of a carboxylic acid, the thus formed reaction product facilitating adherence of the finely subdivided thermoplastic material to the fibers, removing at least a portion of the Water of the thus treated pulp so as to obtain a fibrous mass consisting essentially of the fibers having the thermoplastic material adhered thereto and adapted to be shaped into a shape retaining body.

The present invention is also concerned with a fibrous sheet as an article of manufacture, which fibrous sheet comprises, in combination, a layer of haphazardly arranged fibrous material, a plastic material substantially evenly distributed throughout the layer, and the reaction product of a water-soluble nitrogenous base of high molecular weight and of a water-soluble salt of an organic polycarboxylic acid of high molecular weight interposed between and binding the fibrous and the plastic material to each other.

According to the present invention, the plastic material such as a thermoplastic synthetic material or latex is fixed to the fibers of the pulp by the addition of a high molecular weight, water-soluble nitrogenous base, and of a high molecular, water-soluble salt of an organic polycarboxylic acid.

it would appear, without limiting the invention to this specific explanation, that the nitrogenous base in aqueous solution is attracted to the fibres of the pulp and will react with the polycarboxylic acid under formation of a water-insoluble reaction product which in turn will facili tate adhering of a relatively large proportion of particles of the plastic material to the fibers of the pulp.

As will be described in more detail below, it is frequently desirable to introduce into the pump first the finely subdivided plastic material and the nitrogenous base, and subsequently the salt of the polycarboxylic acid which then will form an insoluble reaction product with the nitrogenous base.

The fibrous material of the pulp may consist of naturat or synthetic cellulose fibers, or also of wood flour or of other vegetable fibers or mineral fibers, as well as of animal fibers, or fully synthetic fibers.

Such fibrous materials also include cotton, cotton linters, sisal, hemp, bagasse, mechanical and chemical wood pulp, regenerated cellulose fibers and the like. Furthermore, fibers of cellulose acetat as well as mineral fibers such as glass or asbestos fibers were successfully treated according to the present invention. In addition, animal fibers such as wool, silk or mohair, are suitable for the purpose of the present invention, as well as fully synthetic fibers of the polyamide, polyacrylonitrile, polyester, polyvinyl alcohol, and other types.

The plastic material which is adhered to the fibers and incorporated in the sheet or the like which is produced according to the present invention, may consist, for instance, of polyvinyl chloride, preferably of the so-called emulsion type and having a low K value, or of other polymerizates or mixed polymerizates on the basis of styrene,

I vinylchloride, vinylacetate, vinylacetal, chloroprene, acrylic ester, and the like, or of polyolefins, or poly-condensation products of the polyamide or polyester type, as well as of latex or butadiene products.

The water soluble high molecular nitrogenous bases which are preferably used according to the present invention include polyethylene imine, polypropylene imine, and polyvinyl amine.

Water-soluble salts of high molecular organic polycarboxylic acids which give good results according to the present invention include the sodium, potassium and ammonium salts of acrylic acid, methacrylic acid, as well as mixed polymerizates of acrylic acid and acrylic acid amide which include a relatively high proportion of carboxyl groups. Thus, according to the present invention the finely subdivided preferably suspended or emulsified plastic material is fixed to the fibers of the pulp by the addition of a water-soluble nitrogenous base of high moleclar weight such as polyethylene imine and of a watersoluble salt of an organic polycarboxylic acid of high molecular weight such as a salt of polyacrylic acid.

In addition thereto, homologues of polyethylene imine or of polyvinyl amine may be used as the water-soluble nitrogenous base, and as water-soluble polycarboxylic acids homologues of polyacrylic acids or their mixed polymerizates or mixed condensates.

However, surprisingly it has been found that the combination of polyethylene imine or the like and of acrylic acid salts or the like will cause a fixing of the suspended synthetic material to the fibers of the pulp. It is also achieved thereby that foam formation is reduced and that the dewatering of the pulp is facilitated. Simultaneously a greater yield of the plastic material is obtained, i.e., a greater proportion of the dispersed plastic material will be adhered to the fibers of the pulp. Thereby not only costs savings are achieved but also very considerable advantages with respect to the further processing of the dewatered pulp, for instance, during pressure-shaping of the same.

Preferably, according to the present invention the polyethylene imine or the like is added to the mixture of pulp and dispersed plastic material in the form of an aqueous solution and an intimate mixture of these ingredients is produced. Thereafter an aqueous solution of a water-soluble salt of polyacrylic acid or the like is added and, in this manner, the dispersed plastic material, preferably thermoplastic material, will be fixed to the fibers together with the reaction product formed of the polyethylene imine and the salt of the polyacrylic acid.

A very good retention of the thermoplastic material is obtained in this manner, with an even distribution of the thermoplastic material in the fibrous structure, as well as favorable conditions for dewatering of the thus treated pulp, for instance on a paper making machine.

The sequence of the addition of the individual components may be varied. However, it is important that one of the two water-soluble reactants, i.e., either the salt of the polycarboxylic acid or the nitrogenous base is the last constituent added to the mixture, after other components already have been mixed well with each other. The precipitation reaction between the polycarboxylic acid salt and the nitrogenous base proceeds quickly and evenly, so that the process of the present invention is also suitable for being carried out in a continuous manner, provided that intensive mixing is arranged in the areas where the various ingredients are introduced into the pulp.

The amount of precipitating agent, i.e., the amount of water-insoluble reaction product formed by reaction of the nitrogenous base and the polycarboxylic acid, generally will be so chosen as to correspond to an amount Cit of nitrogenous base, such as polyethylene imine which equals between 0.3 and 5% of the quantity of dispersed thermoplastic material which is to be incorporated in the finished product. It is possible, but rarely advisable, to increase the amount of polyethylene imine to more than about 5%, and preferably the amount of the water soluble nitrogenous base will be equal to between 0.5 and 2% of the weight of the thermoplastic material which is to be incorporated into the finished product. Since the polycarboxylic acid is to react with the nitrogenous base, the amount of polycarboxylic acid preferably will be close to the stoichiometric equivalent required for reaction with the nitrogenous base. Thus, for instance, when polyethylene imine is to be reacted with the sodium salt of polyacrylic acid, the optimum weight relationship will be about 1 part of polyethylene imine for 2.2 parts of polyacrylic acid. However, these stoichiometric relationships need not be accurately maintained, and thus,

good results are also obtainable when the amount of the polycarboxylic acid salt equals between about 60% and of the stoichiometric equivalent of the nitrogenous base present in the reaction mixture. Preferably, a pH of between 6 and 9 is maintained in the pulp during the treatment thereof and the same pH range should also be maintained during the further processing of the treated pulp, for instance during dewatering.

Depending on the intended further processing and also on the type of dispersed synthetic or thermoplastic ma:

terial which is incorporated into the pulp, it is frequently. advisable to add, in conventional manner, softeners to the pulp-thermoplastic-material mixture. It is preferred to add a softener only after a part of the water of the treated pulp has been removed by mechanical or thermal means. For instance, when it is desired to work up the treated pulp on a paper machine, the softener may be added in the form of an aqueous emulsion by means of a conventional size-press. The proportion of softeners may vary over a wide range. If no suitable applicator device for the softener is available then it is also possible to add the softener to the pulp mixture during, or preferably after, the above-described treatment according to the present invention has been completed. A great number of thermoplastic synthetic materials may be used according to the present invention without the addition of softeners.

The pulp mixture which has been treated according to the present invention, i.e., wherein the reaction between the nitrogenous base and the polycarboxylic acid has been carried out and a relatively large proportion of plastic material has been adhered to the fibrous portion of the pulp, may then be further processed in conventional manner, for instance to sheet-like materials such as paper or cardboard. The precipitation reaction between the base and the acid may be carried out, for instance, in the hollander or in the tub and thus treated pulp is then conveyed in continuous manner or in batches to a paper or cardboard forming machine for further processing. When it is desired to produce a finished product in the form of flakes, then the further processing, i.e., drying, may be carried out in a so-called scoop drier. Pressed bodies may be produced of the pulp which has been treated according to the present invention by shaping the same in a press having liquid permeable portions.

Generally, it may be said that the pulp with the plastic, preferably thermoplastic, material adhering thereto is first subjected to mechanical dewatering, and subsequently to thermal dewatering which may be coupled with the application of pressure and with shaping of the material.

It is also possible to work up the pulp which has been treated according to the present invention so as to produce thereof multi-layer bodies. In such a case, the individual layers of paper or cardboard are superposed and then compressed under application of pressure and heat so that, if desired, simultaneously further reduction in the water-content of the material will take place. Thereby, due to the application of pressure, an increase in the density of the fiber-thermoplastic material body will occur, so that it is possible in this manner, for instance when using polyvinylchloride as the synthetic material, to increase the specific gravity of the thus formed sheet from about 0.7 to about 1.4.

Generally, the pulp concentration at the start of the treatment according to the present invention will be between O.l and 15% preferably between 2 and 6%. These ranges are preferably maintained irrespective of the specific type of fibrous material of the pulp. Of course, during subsequent working up of the treated pulp, for instance on a paper machine, it might become necessary to further dilute the pulp.

Beating should be carried out to between 12 and 60, preferably between 25 and 40 SR.

The proportion of plastic material, particularly synthetic thermoplastic material which is thus introduced into the paper or the like, i.e., into the fibrous mass, of which the sheet-like body is then to be formed, will be between and 80%, preferably between 40 and 60% of the total dry weight of the finished product. In other words, the amount of the added plastic material in the finished product will be between and 400% or preferably between 50 and 200% of the dry weight of the fibrous constituents of the finished material.

As indicated further above, the proportion of Watersoluble nitrogenous base which is to be added preferably will be equal to between 0.3 and 5%, and most preferably will be between 0.5 and 2% of the weight of the dispersed plastic material and, preferably, the nitrogenous base is introduced in the form of 1-5% solution thereof.

The polycarboxylic acid salt is introduced in an amount which should be close to the stoichiometric equivalent of the nitrogenous base or within the range of between 60 and 140% of the stoichiometric equivalent.

The manner in which the mixture which has been formed in the tank or in the hollander is worked up, particularly on a paper machine, will depend on the desired qualities of the final product. For instance, when very thin papers are to be produced, thencorresponding to the operating speed of the paper machine, and also corresponding to the desired weight per m? of the finished product, the pulp and plastic suspension will have to be more strongly diluted than would be required for producing papers of normal, i.e., somewhat higher Weight per m.'-.

The following examples are given as illustrative of the present invention, without, however, limiting the invention to the specific details of the examples.

Example I A bleached mechanical pulp having a fiber density or consistency of about 5% was ground in continuous refiners or similar devices to about 25 SR. An intimate mixture was then formed in a continuous manner of the thus-treated pulp at a rate of about 4- cubic meters per hour, equal to 200 kg. of fibers per hour, and of one cubic meter per hour of a 20% dispersion of a mixed polymerizate on polyvinyl acetate basis which thus contained about 200 kg. of synthetic material per hour. Subsequently about 1.5 kg./hour of polyethylene imine dissolved in 200 liters of water were added and the thus formed mixture was passed through a pulp pump in order to obtain an even distribution of the various components of the mixture. Thereafter the pulp mixture was diluted with water to a pulp consistency of about 2% and then, by means of an injector, about 1 mfi/hour of a 0.2% aqueous solution of the sodium salt of polyacrylic acid, equal to about 2 kg. of sodium polyacrylate per hour, were introduced. The aqueous solution of polyacrylic acid was adjusted to a pH of between 8 and 9. The thus formed mixture was then diluted to a pulp consistency of about 0.5% and subsequently worked up on a paper machine to a paper having a weight of 350 gr./m. The thus formed paper sheet contained about 45% per weight of the synthetic plastic material.

Example H A mixture of pulp, of a dispersed, softened mixed polymerizate on the basis of polyvinylacetate, of polyethylene imine and of sodium polyacrylate was formed as described in Example I. The thus formed mixture was then diluted with water to a pulp consistency of 0.6%. The thus diluted and treated pulp was passed continuously to the dewatering screen of a cardboard machine. In conventional manner about 20 layers of the thus formed sheet weighing about 75 gr./m. were united on a couch cylinder. After withdrawal from the couch roller, moist plates were obtained which were then dried in a hot air tunnel. In this manner, cardboard plates were obtained having a weight of about 1500 gr./m. and containing between 40 and 42% or" the synthetic material.

6 Example 111 100 kg. of unbleached mechanical pulp were sus pended in water in a concentration of 6% and beaten in a hollander to about 30 SR. Thereafter 150 kg. of emulsion type polyvinylchloride having a K value of about 60 were introduced into the hollander in the form of a fine powder and well mixed into the pulp. As further additions, 3 kg. of polyethylene imine were introduced in the form of a 1% aqueous solution, and after thorough mixing, a 0.5% aqueous solution of 6 kg. of the ammonium salt of polyacrylic acid was added. It is important to form immediately upon introduction of the polyacrylic acid salt an intimate mixture of the polyacrylic acid salt and the previously formed mixture, and therefore, unless devices are available which have a very strong mixing effect, the addition of the polyacrylic acid salt has to be carried out rather slowly.

The thus formed mixture was then immediately worked up on a paper machine to a paper Web having a weight of 150 -gr./m. A size press arranged within the paper machine was used to apply an amount of dibutyl phthalate which equals 20% of the quantity of synthetic thermoplastic material which has been incorporated in the paper. The dibutyl phthalate was introduced at both faces of the paper web in the form of a 15% aqueous emulsion. The finished paper contained 55% thermoplastic material. Thereafter 10 sheets of the thus formed paper were superposed and compressed at a pressure of kgjcm. and at a temperature of 170 C. so as to obtain a laminated structure having a density of 1.4. Due to the relatively high temperature of 170 C., gelatinization of the synthetic materials in the paper will occur and thus a substantially pore-free laminated body will be produced.

Example IV A pulp having a consistency of 2% was formed of 30 parts per weight of asbestos fibers, 40 parts per weight of unbleached chemical wood pulp (40 SR) and 30 parts per weight of mechanical pulp. To the thus formed mixed pulp, 150 parts (tdry substance) of a styreneacrylic acid nitrile mixed polym-erizate (:10) were added in the form of a 30% aqueous dispersion. Thereafter, a 5% aqueous solution, containing 1.5 parts per weight of polyethylene imine was added to, and thoroughly mixed with, the pulp. As final addition a 0.1% aqueous solution of an acrylic acid-acrylic acid amide mixed polymerizate (4: 1) including 2 parts per weight of the mixed polymerizate in the form of its sodium salt was added. After thorough mixing, the thus treated pulp was dewatered on a screen so as to form thereof plates having a dry weight of between 2.5 and 3 kg./m. The plates which were still moist were then dried and compressed in a m ulti-layer hydraulic press at a pressure of 20 kg./cm. and at a temperature of 80 C. until the plates were substantially completely dry. Thereafter, the plates were further compressed at a pressure of 50 kg./cm. and at a temperature of C. until the specific gravity of the plates had risen to 1.25. The thus formed plates contained.55% of the thermoplastic material and were used as lining or covering for walls, furniture or the like.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applicaitons without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. A fibrous sheet, comprising in combination, a layer of haphazardly arranged fibrous material; at least one plastic material selected from the group consisting of polyethylene, polypropylene, polyamides, polyesters, and polymerizates and mixed polymerizates of vinylchloride, vinylidenechloride, vinylacetate, vinylacetal, chloroprene, latex, styrene, butadiene, acrylic acid ester and acrlyonitrile substantially evenly distributed throughout said layer; and the reaction product of a water-soluble nitrogenous base of high molecular weight selected from the group consisting of polyethylene irnine, polypropylene imine and polyvinyl amine, and of a water-soluble salt of an organic polycarboxylic acid of high molecular weight selected from the group consisting of sodium, potassium and ammonium salts of acrylic acid and methacrylic acid, and mixed polymerizates of acrylic acid and acrylic acid amide containing a relatively large proportion of carboxyl groups interposed between and binding said fibrous and said plastic material to each other.

2. A fibrous sheet, comprising in combination, a layer of haphazardly arranged fibrous material; at least one plastic material in an at .ount equal to between about 25% and 400% of the dry weight of said fibrous material, said plastic material being selected from the group consisting of polyethylene, polypropylene, polyamides, polyesters, and polymerizates and mixed polymerizates of vinylchloride, vinylidenechloride, vinylacetate, vinylacetal, chloroprene, latex, styrene, butadiene, acrylic acid ester, and acrylonitrile substantially evenly distributed throughout said layer; and the reaction product of an amount of a water-soluble nitrogenous base of high molecular weight equal to between about 0.3 and of the Weight of said plastic material, said nitrogenous base being selected from the group consisting of polyethylene irnine, polypropylene imine and polyvinyl amine, and of an amount of a water-soluble salt of an organic polycarboxylic acid of high molecular weight equal to between about 60% and 140% of the stoichiometrically equivalent amount relative to said nitrogenous base, said salt being selected from the group consisting of the sodium, potassium and ammonium salts of acrylic acid and methacrylic acid, and mixed polymerizates of acrylic acid and acrylic acid amide containing a relatively large proportion of carboxyl groups interposed between and binding said fibrous and said plastic material to each other.

3. A fibrous sheet, comprising in combination, a layer of haphazardly arranged fibrous material selected from the group consisting of animal, vegetable, mineral and synthetic organic fibers; at least one thermoplastic material in an amount equal to between about and 400% of the dry weight of said fibrous material, said plastic material being selected from the group consisting of polyethylene, polypropylene, polyamides, polyesters and polymerizates and mixed polymerizates of vinylchloride, vinylidenechloride, vinylacetate, vinylacetal, chloroprene, latex, styrene, butadiene, acrylic acid ester and acrylonitrile substantially evenly distributed throughout said layer; and the reaction product of an amount of a water-soluble nitrogenous base of high molecular weight equal to between about 0.3 and 5% of the weight of said plastic material, said nitrogenous base being selected from the group consisting of polyethylene irnine, polypropylene irnine and polyvinyl amine, and of an amount of a watersoluble salt of an organic polycarboxylic acid of high molecular Weight equal to between about 60% and 140% of the stoichiometrically equivalent amount relative to :said nitrogenous base, said salt being selected from the group consisting of sodium, potassium and ammonium salts of acrylic acid and methacrylic acid, and mixed polymerizates of acrylic acid and acrylic acid amide containing a relatively large proportion of carboxyl groups interposed between and binding said fibrous and said thermoplastic material to each other.

4. In a method of producing a shaped body consisting essentially of an intimate mixture of a fibrous material and a thermoplastic material interposed between and .adhering to the fibers of said fibrous material, the steps weight selected from the group consisting of polyethyleneimine, polypropylene imine and polyvinyl amine, and a i water-soluble salt of a polycarboxylic acid of high moleclLllBI weight selected from the group consisting of sodium, potassium and ammonium salts of acrylic acid and methacrylic acid, and mixed polymerizates of acrylic acid and acrylic acid amide containing a relatively large proportion of carboxyl groups, so as to form on said fibers a water insoluble reaction product of said nitrogenous base and said salt of a carboxylic acid, the thus formed reaction product facilitating adherence of said finely subdivided thermoplastic material to said fibers; and removing at least a portion of the water of the thus treated pulp so as to obtain a fibrous mass consisting essentially of said fibers having said thermoplastic material adhered thereto and adapted to be shaped into a shape retaining body.

5. In a method of producing a sheet-like body consisting essentially of an intimate mixture of a fibrous material and a thermoplastic material interposed between and adhering to the fibers of said fibrous material, the steps of introducing into a fibrous pulp consisting essentially of a suspension of fibers in water a finely subdivided thermoplastic material selected from the group consisting of polyethylene, polypropylene, polyamides, polyesters, and polymerizates and "mixed polymerizates of vinylchloride, vinylidenechloride, vinylacetate, vinylacetal, chloroprene, latex, styrene, butadiene, acrylic acid ester, and acrylonitrile, a water-soluble nitrogenous base of high molecular weight selected from the group consisting of polyethylene irnine, polypropylene imine and polyvinyl amine and a water-soluble salt of a polycarboxylic acid of high molecular weight selected from the group consisting of the sodium, potassium and ammonium salts of acrylic acid and methacrylic acid, and mixed polymerizates of acrylic acid and acrylic acid Iamide containing a relatively large proportion of carboxyl groups, said salt of a carboxylic acid being introduced subsequently to the introduction of said nitrogenous base, so as to form on said fibers a water insoluble reaction product of said nitrogenous base and said salt of a carboxylic acid, the thus formed reaction product facilitating adherence of said finely subdivided thermoplastic material to said fibers; removing at least a portion of the water of the thus treated pulp so as to obtain a fibrous mass consisting essentially of said fibers having said reaction product and said thermoplastic material adhered thereto; and forming a sheet of the thus obtained fibrous mass.

6. In a method of producing a sheet-like body consisting essentially of an intimate mixture of a fibrous material and a thermoplastic material interposed between and adhering to the fibers of said fibrous material, the steps of introducing into a fibrous pulp consisting essentially of a suspension of fibers in Water having a fiber concentration of between 0.1 and 15% a finely subdivided thermoplastic material selected from the group consisting of polyethylene, polypropylene, polyamides, polyesters, and polymerizates and mixed polymerizates of vinylchloride, vinyliidenechloride, vinylacetate, vinylacetal, chloroprene, latex, styrene, butadiene, acrylic acid ester and acrylonitrile in an amount equal to between 25 and 400% of the dry weight of said fibers; a water-soluble nitrogenous base of high molecular weight selected from the group consisting of polyethylene irnine, polypropylene imine and polyvinyl amine, in an amount equal to between 0.3 and 5% of the Weight of said finely subdivided thermoplastic material and a water-soluble salt of a polycarboxylic acid of high molecular weight selected from the group consisting of sodium, potassium and ammonium salts of acrylic acid and methacrylic acid, and mixed polymerizates of acrylic acid and acrylic acid amide containing a relatively large proportion of carboxyl groups in an amount equal to between 60% and 140% of the stoic'hio metrically equivalent amount relative to said nitrogenous base, so as to form on said fibers a Water insoluble reaction product of said nitrogenous base and said salt of a carboxylic acid, the thus formed reaction product facilitating adherence of said finely subdivided thermoplastic material to said fibers; removing at least a portion of the water of the thus treated pulp so as to obtain a fibrous mass consisting essentially of said fibers having said thermoplastic maten'al adhered thereto; and forming a sheet of the thus obtained fibrous mass.

7. In a method of producing a sheet-lilce body consisting essentially of an intimate mixture of a fibrous material and a thermoplastic material interposed between and adhering to the fibers of said fibrous material, the steps of introducing into a fibrous pulp consisting essentially of a suspension of fibers in water having a fiber concentration of between 2-6% a finely subdivided thermoplastic material selected from the group consisting of polyethylene, polypropylene, polyamides, polyesters and polymerizates and mixed polymerizates of vinylchloride, vinylidenechloride, vinylacetate, vinylacetal, chloroprene, latex, styrene, butadiene, acrylic acid ester and acrylonitrile in an amount equal to between 50200% of the dry weight of said fibers, a Water-soluble nitrogenous base of high molecular weight selected from the group consisting of polyethylene imine, polypropylene imine and polyvinyl amine, in an amount equal to between 0.52% of the Weight of said finely subdivided thermoplastic material and a Water-soluble salt of a polycarboxyl-ic acid of high molecular Weight selected from the group consisting of sodium, potassium and ammonium salts of acrylic acid and methacrylic acid, and mixed polymerizates of acrylic acid and acrylic acid amide containing a relatively large proportion of carboxyl groups in an amount substantially equal to the stoichiometrically equivalent amount relative to said nitrogenous base, so as to form on said fibers a water insoluble reaction product iOf said nitrogenous base and said salt of a carboxy-lic acid, the thus formed reaction product facilitating adherence of said finely subdivided thermoplastic material to said fibers; removing 45 at least a portion of the water of the thus treated pulp so as to obtain a fibrous mass consisting essentially of said fibers having said thermoplastic material adhered thereto; and forming a sheet of the thus obtained fibrous 'rnass.

8. In a method of producing a sheet like body consisting essentially of an intimate mixture of a fibrous material and :a thermoplastic material interposed between and adhering to the fibers of said fibrous material, the steps of introducing into a fibrous pulp consisting essentially of a suspension of fibers in water having a fiber concentration of between 0.1 and 15% a finely subdivided thermoplastic material selected from the group consisting of polyethylene, polypropylene, polyamides, polyesters and polymerizates and mixed polymerizaws of vinylchloride, vinylidenechloride, vinylacetate, vinylacetal, chloroprene, latex, styrene, butadiene, acrylic acid ester and acrylonitrile in an amount equal to between 25 and 400% of the dry Weight of said fibers, tan aqeuous solution containing between 1 and 5% of a Water-soluble nitrogenous base of high molecular Weight selected from the group consisting of polyethylene imine, polypropylene imine and polyvinyl amine, in an amount equal to between 0.3 and 5% of the Weight of said finely subdivided thermoplastic material and a Water-soluble salt of a polycarboxy-lic acid of high molecular weight selected from the group consisting of sodium, potassium and ammonium salts of acrylic acid and methacrylic acid, and mixed polymerizates of acrylic acid and acrylic acid amide containing a relatively large proportion of carboxyl groups in an amount equal to between and of the stoichiometrically equivalent amount relative to said nitrogenous base, so as to form on said fibers a Water insoluble reaction product of said nitrogenous base and said salt of a carboxylic acid, the thus formed reaction product facilitating adherence of said finely subdivided thermoplastic material to said fibers; removing at least a portion of the water of the thus treated pulp so as to obtain a fibrous mass consisting essentially of said fibers having said thermoplastic material adhered thereto; and forming a sheet of the thus obtained fibrous mass.

References Cited in the file of this patent UNITED STATES PATENTS 2,686,121 Lathain et a1 Aug. 10, 1954 2,721,140 Weisgerber Oct. 18, 1955 2,910,399 Jordan M Oct. 27, 1959 FOREIGN PATENTS 467,655 Italy Dec. 14, 1951 601,461 Canada July 12, 1960 

1. A FIBROUS SHEET, COMPRISING A COMBINATION, A LAYER OF HAPHAZARDLY ARRANGED FIBROUS MATERIAL; AT LEAST ONE PLASTIC MATERIAL SELECTED FROMTHE GROUP CONSISTING OF POLYETHYLENE, POLYPROPYLENE, POLYAMIDES, POLYESTERS, AND POLYMERIZATES AND MIXED POLYMERIZATES OF VINYLCHLORIDE, VINYLIDENECHLORIDE, VINYLACETATE, VINYLACETAL, CHLOROPRENE, LATEX, STYRENE, BUTADIENE, ACRYLIC ACID ESTER AND ACRLYONITRILE SUBSTANTIALLY EVENLY DISTRIBUTED THROUGHOUT SAID LAYER; AND THE REACTION PRODUCT OF A WATER-SOLUBLE NITROGENOUS BASE OF HIGH MOLECULAR WEIGHT SELECTED FROM THE GROUP CONSISTING OF POLYETHYLENE IMINE, POLYPROPYLENE IMINE AND POLYVINYL AMINE, AND A WATER-SOLUBLE SALT OF AN ORGANIC POLYCARBOXYLIC ACID OF HIGH MOLECULAR WEIGHT SELECTED FROM THE GROUP CONSISTING OF SODIUM, POTASSIUM AND AMMONIUM SALTS OF ACRYLIC ACID AND METHACRYLIC ACID, AND MIXED POLYMERIZATES OF ACRYLIC ACID AND ACRYLIC ACID AMIDE CONTAINING A RELATIVELY LARGE PROPORTION OF CARBOXYL GROUPS INTERPOSED BETWEEN AND BINDING SAID FIBROUS AND SAID PLASTIC MATERIAL TO EACH OTHER. 